Rollup merge of rust-lang#70385 - RalfJung:miri-nits, r=eddyb

Miri nits: comment and var name improvement

r? @eddyb

src/librustc_mir/const_eval/machine.rs

@@ -178,7 +178,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter {
 
     type MemoryMap = FxHashMap<AllocId, (MemoryKind<!>, Allocation)>;
 
-    const GLOBAL_KIND: Option<!> = None; // no copying of globals allowed
+    const GLOBAL_KIND: Option<!> = None; // no copying of globals from `tcx` to machine memory
 
     // We do not check for alignment to avoid having to carry an `Align`
     // in `ConstValue::ByRef`.
@@ -350,15 +350,15 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter {
         memory_extra: &MemoryExtra,
         alloc_id: AllocId,
         allocation: &Allocation,
-        def_id: Option<DefId>,
+        static_def_id: Option<DefId>,
         is_write: bool,
     ) -> InterpResult<'tcx> {
         if is_write && allocation.mutability == Mutability::Not {
             Err(err_ub!(WriteToReadOnly(alloc_id)).into())
         } else if is_write {
             Err(ConstEvalErrKind::ModifiedGlobal.into())
-        } else if memory_extra.can_access_statics || def_id.is_none() {
-            // `def_id.is_none()` indicates this is not a static, but a const or so.
+        } else if memory_extra.can_access_statics || static_def_id.is_none() {
+            // `static_def_id.is_none()` indicates this is not a static, but a const or so.
             Ok(())
         } else {
             Err(ConstEvalErrKind::ConstAccessesStatic.into())

src/librustc_mir/interpret/machine.rs

@@ -215,7 +215,7 @@ pub trait Machine<'mir, 'tcx>: Sized {
         _memory_extra: &Self::MemoryExtra,
         _alloc_id: AllocId,
         _allocation: &Allocation,
-        _def_id: Option<DefId>,
+        _static_def_id: Option<DefId>,
         _is_write: bool,
     ) -> InterpResult<'tcx> {
         Ok(())

src/librustc_mir/transform/const_prop.rs

@@ -172,7 +172,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine {
 
     type MemoryMap = FxHashMap<AllocId, (MemoryKind<!>, Allocation)>;
 
-    const GLOBAL_KIND: Option<!> = None;
+    const GLOBAL_KIND: Option<!> = None; // no copying of globals from `tcx` to machine memory
 
     const CHECK_ALIGN: bool = false;
 
@@ -274,7 +274,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine {
         _memory_extra: &(),
         _alloc_id: AllocId,
         allocation: &Allocation<Self::PointerTag, Self::AllocExtra>,
-        def_id: Option<DefId>,
+        static_def_id: Option<DefId>,
         is_write: bool,
     ) -> InterpResult<'tcx> {
         if is_write {
@@ -285,7 +285,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine {
         if allocation.mutability == Mutability::Mut {
             throw_machine_stop_str!("can't eval mutable globals in ConstProp");
         }
-        if def_id.is_some() && allocation.relocations().len() > 0 {
+        if static_def_id.is_some() && allocation.relocations().len() > 0 {
             throw_machine_stop_str!("can't eval statics with pointers in ConstProp");
         }